Methods of coating sheet material with particulate material



1955 P. A. MARSELL ETAL 2,701,774

METHODS OF COATING SHEET MATERIAL WITH PARTICULATE MATERIAL OriginalFiled Nov. 3, 1947 4 Sheets-Sheet l Fie. 1

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1955 P. A. MARSELL ETAL 2,701,774

METHODS OF COATING SHEET MATERIAL v WITH PARTICULATE MATERIAL OriginalFiled Nov. 3, 1947 4 Sheets-Sheet 2 G 1 .1 1 A. B F 4 X |I|./#Xiiiiliil: I}. V s I 7 L\ 5 9 o ow 3 z 3 6 3 3 IF s w m 6 4 v F m 8 l 92 Ow A 1 w s I 15: ,RA 0 o 0/ o 0 MM M .w----v. g 5 "w w m m w 1 J T F Wmu AP P. A. MARSELL ETAL METHODS OF COATING SHEET MATERIAL Feb. 8, 1955WITH PARTICULATE MATERIAL, Original Filed NOV. 3, 1947 4 Sheets-Sheet 3Fia. 8

Feb. 8, 1955 P. A. MARSELL ET AL- METHODS OF COATING SHEET MATERIALWITHPARTICULATE MATERIAL 1947 4 Sheets-Sheet 4 Original Filed Nov. 3,

United States Patent METHODS OF COATING SHEET MATERIAL WITH PARTICULATEMATERIAL Philip A. Mai-sell, Emsworth, and Charles H. Teller, MountLebanon, Pa., assignors to Koppers Company, Inc., a corporation ofDelaware Original application November 3, 1947, Serial No.

783,710. Divided and this application November 29 1950, Serial No.262,618

2 Claims. (Cl. 117-24) This invention relates to improvements in methodsof and means for applying solid particulate material to surfaces'to becoated therewith. More particularly the invention relates to conveyanceof such material and uniform distribution thereof on said surfaces toprovide articles uniformly coated with the particulate material.

Various means have been employed prior to the present invention, wherebysurfaces have been coated with solid particulate materials such asgranules, dusts, or aggregate. Such surfaces have been precoated with anadhesive bonding material and thereafter granules have been projected ordropped onto the precoated surfaces. For large scale production, handsprays have been more or less inefiicient and inadequately effective inuniformly distributing the granules. Mere dropping of granules on anadhesive coated object causes too close packing and in most instancesthere is insufiicient force'to cause proper sticking and embedding. Theuse of rolls to press the granules into an adhesive coating has notproved practical particularly for such objects as corrugated sheets orother articles with irregular surfaces.

In many suggested means for coating sheet materials, for instance, onlyone side of a sheet is coated at a time and some particular means arefrequently required to provide, with somewhat complex or sensitivemechanisms, a turbulent suspension or stream of particles, and means forremoving excess granules. Also, usually, a single means is provided forapplying particulate material without regard. to the characteristics ofthe particles of such material.

The present invention provides means for overcoming various difficultiesof the prior art.

An object of this invention is to provide improvements.

in methods of and means for applying solid particulate material tosurfaces to be coated therewith. Another object is to provide improvedmethods and means whereby, in a continuous production of coatedarticles, such surfaces are uniformly coated over their entire areaswith solid particulate material. A further object is to providerelatively simple means for bringing into adhesive engagement withsheets or boards of extensive area, solid particulate material and tocoat the entire area uniformly with said material. An object is also toprovide improved means for selectively applying solid particulatematerial of different specific gravities and varying as to othercharacteristics.

In the invention to be described more particularly below, as applied tocoating of sheets or boards, the articles to be coated with solidparticulate material are precoated with an adhesive layer or film toprovide a bonding means for the solid particles. The entire surface ofthe precoat is preferably maintained uniformly sticky while the articlesare conveyed in succession, continuously or intermittently, through anenclosure past improved means for applying solid particulate matter in amanner whereby the particles are made to cover the sticky surfaceuniformly. In said improved means, particles are initially permitted tofall vertically and are then forcibly diverted in a horizontaldirection, in a suspension of uniform concentration, toward an adhesivecoated surface passing across the path of said particles.

Solid particulate material employed includes granules or aggregate ofany suitable size in the range of about to 100 mesh and preferably 10 or20 to 40 or 50 mesh. The particles of the material have surfaces whichhave anyone or more of the following characteristics: curved 2,701,774Patented Feb. 8, 19 55 and shell-like, fiat, approximately even planes,very uneven, rough, or irregular. The granules may be made up of naturalgranules, artificially colored granules, synthetic granules or mixturesof granular substances. Materials most commonly used are slate,greenstone, chert, flint,

' quartzite, rhyolite, quartz sand, quartz river gravels, limestone,feldspar, granite, ore tailings, slag, shale, crushed brick and tile,mica, talc, and foliated talc. fiber, paper stock, abrasive dusts,organic dusts, and metal powders may also be employed.

Further details of the present invention are described hereinbelow andare shown in the accompanying drawings ment;

Fig. 6 is a front elevational view of another element in said means;

Fig. 7 is a side elevational view of a carrier means or rack for sheetsto be coated with particulate material;

Fig. 8 is an elevational view, partly in section, of a plant arrangementin which selective application of particles to sheets is made possible;

Fig. 9 is a horizontal section of a portion of the apparatus shown inFig. 8, taken on line 99;

Fig. 10 is an enlargement of a portion of the view of the apparatusshown in Fig. 2; and

Fig. 11 illustrates diagrammatically the operation of one type of plantin which the said means are employed.

Similar parts of the apparatus are designated by the same referencecharacters in the various figures.

Referring to Figures 1 to 5, there is shown an elongated receptacle lfor solid particulate material. The receptacle has means whereby theparticulate material may be discharged therefrom in a verticallydescending, curtain-like stream and means for controlling the thicknessof said stream. In the receptacle shown, a rigidly positioned top 2 anda rigidly positioned bottom 3 transversely inclined (Fig. 5 toward aside wall 4 functioning as an adjustable gate, serve as means forproviding the above-described stream. The upper edge 5 of the side 4 ishinged to permit the movement of its lower edge 6 toward or away fromthe bottom 3. When the side wall or gate 4 is closed, the edge 6 is inthe plane of the surface of the bottom 3 and adjacent the lower edge 7thereof. When the edge 6 is seated on or held tightly against thebottom, the particulate material 8 is maintained in the receptacle 1.

Adjustable means provided for controlling the thickness of the stream ofparticulate material flowing out of the receptacle 1 on opening the gate4, comprises a handwheel 9 mounted on a yoke 10 and in threadedengagement with a rod 11 longitudinally movable by turning thehandwheel. The rod 11 operates a lever 12 which in turn operates thegate 4.

Upon opening the gate 4 an outlet slot for particulate material isformed which permits the material to fall by gravity over the edge 7 ofthe bottom 3. Means are provided for directing the particulate material,substantially at the beginning of the formation of a curtain-likestream, towards a surface to be coated with said material, which surfaceis moved horizontally or vertically across the path terial, whereby anair-blast can be directed across the.

width of the descending stream of said material. The edge 16 of the flapor air gate 14 is preferably positioned beyond the vertical path of theparticulate material so Asbestos that particles reaching the surface ofthis flap can at least be momentarily retained in the path of the blastand can be swept thereby toward a surface to be covered.

Adjustable means are provided for controlling the width of the air slot.Such means comprise a handwheel 17'mounted on a yoke 18 and in threadedengagement with a rod 19 longitudinally movable by turning saidhandwheel 17. The rod 19 is linked with one end of an arm 20. The otherend of this arm is attached to the flap or air gate 14.

Stitfener rods 21 aid in supporting and in maintaining the inclinedbottom 3 and the wall 2 rigidly in place.

Air is blown under pressure into the compartment 13 from an air flue 22through an opening 23 in the wall 15, which registers with an opening 24in the flue 22. The air flue 22 and the receptacle 1 with its associatedmeans are mounted on the vertical wall 25 of an enclosure or housing inwhich solid particulate material is applied to a sheet.

Though a sheet may be moved vertically in the path of particulatematerial projected from a receptacle 1, it is found highly convenientand effective to convey such sheet in vertical position horizontallypast a plurality of such particle-applying means arranged in a manner tobe described and as shown in Fig. 1. In such instances, the receptacle 1may be considered as an in clined chute closed at its lower end by aremovable plate 27. The angle of such chute with the horizontal ispreferably greater than the angle of repose or angle of friction of theparticulate material used.

The receptacles 1 are shown in Fig. 1 as parallel extensions ofinclined, branch chutes 28 depending from a main vertical chute 29provided at its lower end with a clean-out door 2%. The branch chutesare vertically spaced apart, and each of a plurality of diagonallyarranged air outlets 24 in the vertical air flue 22 is connected to anair compartment 13 of a granule-applying unit embodying thereceptacle 1. It is readily seen that with the receptacles 1 in theposition shown, the solid particulate material is projectedsubstantially horizontally in a plurality of inclined, substantiallyparallel planes or strata, vertically spaced apart. The planes ofprojected particles extend toward the face of a sheet while beingcoated, and the particles impinge in strata extending diagonally acrossthe face. The units 1 are so positioned that the particles in the loweredge of each stratum above the lowermost stratum are below the particlesin the upper edge of the next subjacent stratum. In other words theparticles are applied to the surface of a sheet in overlapping zones asthe surface is moved horizontally across the paths of the projectedparticles.

As shown in Figs. 2 and 8, in the coating of articles such as sheets, onboth sides, the particle-applying units in the arrangement shown in Fig.1, may be placed on either side of an article in a housing having sidewalls 30 and 31, and a track 32 running midway between the walls at theceiling. A rack 33 (Fig. 7) suspended from a roller 34, movable alongthe track 32, is provided for carrying an article such as a sheet 35.

The rack comprises a trapezoidal frame having side bars 36 and 37, andtapering from the lower end to a top cross bar 38. Bracket means 39 atthe lower end of the frame serves to support the lower edge of a sheet35, under treatment, spaced from the plane of the side bars 36 and 37 sothat the sheet may lean with its upper end against the frame, as shownin Fig. 8. Metal rods 3%, each having one end hinged to an arm 40 on oneside bar 36, and the other end resting on an arm 41 on side bar 37, arebrought across the free side of a sheet, to keep the sheet from beingaccidentally pushed from a rack when it is being moved on the track 32.On this rack a sheet is practically completely exposed to impingement byparticulate material on both sides.

In the coating of sheets with solid particulate material, it is foundadvantageous to employ one of two types of means depending upon thespecific gravity and structure or other characteristics of the particlesof such material. In the application of heavier materials, such as slateparticles for instance, the use of the means shown in Figs. 3, 4 and ispreferred. In the application of lighter materials, especially when theparticles are fluffy, or leafy, or show a tendency to float in or toremain in suspension in air, or are likely to pack in chutes, it ispreferred to use a means shown in Figs. 1, 2, 6, and 8.

The last named means includes a chute 45 for particulate materialassociated with an air flue 46. This means may be placed as shown inFig. 2, on either side of the track 32 within the walls 30 and 31 of theenclosure, and adjacent the receptacles 1. Substantially throughout itsheight within the enclosure, the wall 47 of the flue 46, facing the pathof a sheet conveyed on the track 32 through the enclosure, is providedwith a plurality of small openings 48 uniformly spaced one above theother. The chute 45 is fastened to the Wall 47 of the flue 46 and isprovided with a slot 49 in a wall 50 opposite the wall 47. The slot 49extends vertically substantially the entire length of the chute 45inside the enclosure, and is slightly wider than the diameter of theopenings 48. The centers of the openings 48 and the center line of theslot 49 are in a plane substantially perpendicular to the line of travelof a sheet under treatment in the enclosure. Particles of theparticulate material are projected in this plane by an air blast in theflue 46 through the openings 48.

The width of the upper end of the chute 45 is substantially the width ofthe flue 46. The side walls 51 and 52 of the chute 45, as they extenddownwardly, converge so that at the bottom of the enclosure the distancebetween these walls is substantially the width of the slot 49. The widthof the flue 46 is substantially uniform throughout its height in theenclosure. The convergence of the walls 51 and 52 tends to maintain theparticles of particulate material passing down the chute 45 at about thesame concentration throughout the height of this chute. ble to provide auniform dispersion or suspension of particles adjacent the entiresurface of a sheet as it passes in front of the slot 49.

Baffles 53 are provided in the chute 45 to break the fall of theparticles of particulate material and thus decrease their verticalvelocity so that they are more readily forced horizontally toward asheet. The baffles 53, as shown in Fig. 6, extend partly across thechute 45 at intervals alternately from the walls 51 and 52. They areinclined downwardly from said Walls, and the free edge of each ispositioned just past, or substantially at, the center line of the slot,49. When the particulate material employed consists of particles of alight flaky material, such as mica, or material of relatively lowdensity such as certain fibrous substances, the baffles are notessential. In such instances, the baffles may be omitted as indicated inFig. 10.

In the use of the above two types of means for applying particulatematerial to both sides of a sheet, the air and particle outlets of suchmeans on one side of the line of travel of a sheet are preferablysubstantially the same distance from said line as the air and particleoutlets, respectively, of a corresponding means on the other side ofsaid line, as shown in Fig. 2.

The flues 46 and the fiues 22 on either side of the enclosure areconnected at their upper ends to a common duct 54 by branch ducts 55 and56 through which air or other gaseous fluid pass under'pressure. To stopor permit passage of air selectively to one or another of theparticle-applying means, slide valves 57 and 58 are provided. These areshown in enlargement in Fig. 10 in which the flue connections areindicated for particleapplying means on one side of the enclosure. Anair duct 59 is connected to the top end of the flue 46. The slide valve58 is employed to regulate the supply of air from the duct 59 into theflue 46. A duct 60 connects the duct 59 to the top end of the flue 22.The slide valve 57 situated in the duct 60 regulates the supply of airfrom the duct 59 into the flue 22, to which the particle-applying meansshown in Figs. 3, 4 and 5 is connected.

For selectively feeding the chutes 45 and the receptacles 1' withparticulate material, means are provided such as that shown in Figs. 8and 9. The chutes 29 extend downwardly from the bottom of a hopper 65.The chutes 45 extend downwardly from the bottom of a hopper 66. Thebottom of the hopper 65 is provided with inclined Walls 67 and 68positioned to direct particulate material into the chutes 29 on bothsides of the enclosure within the walls 30 and 31. A belt conveyor 69 inassociation with a dividingwall, 70, and inclined walls71 and.72 in thebottom of hopper 66 distribute particulate material to they two chutes45. Positioned above the conveyor 69 is a In other Words, it is madepossi hopper 73 for feeding particulate material to the conveyor.Particulate material on the conveyor is levelled by means of a levellingmeans 74, as the material is moved to the right. A chute 75 is providedfor spillage.

Means are provided for continuously circulating the particulate materialfrom the enclosure in which the material is applied to the sheets, to'the selected hopper. A pit 76 is positioned beneath the enclosure tocollect excess particulate material that does not adhere to a sheet. Ascrew conveyor 77 driven by a motor 78 passes the material from thebottom of the pit 76 to a bucket conveyor 79 which raises the materialto a level above the hoppers 65, 66 and 73.

From the bucket conveyor the particulate material is dumped on aninclined vibrating screen 80. Any material retained on the screen isdiscarded through a chute 81. Material passing through the screen runsinto a feed chute 82 from which it is selectively fed to the hopper73-or the hopper 65. A gate 83 when opened permits material to fall fromthe chute 82 into the hopper 73. A gate 84 when opened permits materialto fall from the chute 82 into the hopper 65. The single chute 82,therefore, serves to feed selectively one or the other of the types ofparticulate material adapted to be employed in the two particle-applyingmeans in the enclosure in which a sheet is coated.

in the coating of sheet material with solid particles of substancesindicated hereinabove, a sheet is first coated with a film or layer of acomposition that will serve to bind the particles to the surface. Such acomposition may be a glue or an adhesive, including a synthetic ornatural resin-containing material, a bitumen-containing material, or thelike, which may be applied by spraying, brushing, or dipping. Thisprecoating may be thermoplastic or thermosettihg and may be applied as asolution from which the solvent may be evaporated, or as a hardenablemolten, substance.

Fig. 11 serves as a flow diagram to illustrate a plant and itsoperation, in connection with the improved means described, foruniformly coating sheets with solid particulate material. In such aplant it is assumed that a metal, wooden or composition sheet materialeither corrugated or flat and suitable for siding or roofing in buildingor other structures, is precoated with a bituminous or other coatingthat can be rendered soft or sticky by heat.

In such instance, the precoated sheets are passed through an elongatedtunnel 90 on a continuous conveyor 91 comprising an overhead track fromwhich are hung racks such as illustrated in Figs. 7 and 8. A sheet issupported on its end in a substantially vertical position on a rack andis passed successively through a heating section or chamber 92 in saidtunnel, a section or chamber 93 (also termed a dusting chamber) in whichsolid particulate material is applied, and a cooling section or chamber94. The courses of the various air currents are indicated by arrowsexplained in the legend.

The precoated sheet is heated uniformly over the entire coated surfacein the chamber 92 by a current of air heated in a furnace 95 and kept incirculation by a fan 96 to render the surface preferably uniformlysticky, as in a manner set forth, for instance, in a U. S. patentapplication of M. I. Dorfan, Serial No. 708,096, filed November 6, 1946,now Patent 2,536,042. As further illustrated in said application, thesurface is maintained sticky over its entire area in the dusting chamber93 by circulation of heated air therethrough, and after applying thedust (solid particulate material) the sheet is cooled by a current ofcooling air in chamber 94, to set the coating. The sheets emerging fromthe chamber 94 are removed from the conveyor 91 in substantiallyfinished form.

Dust laden air from the chamber 93 may be treated to recover the dust bymeans of apparatus diagrammatically illustrated in the above Fig. 11,and shown in detail in the above application.

In applying the dust, hot air may be used to pro ect the particles ontoa thermoplastic surface. Hot air Wlll tend to preheat the particles sothat they may more readily penetrate the surface of a thermoplasticcoating. Such air may be withdrawn from the roof of chamber 93 by a fan97, and by said fan forced into the abovedescribed particle-applyingmeans.

For coating sheets placed in vertical position and moving horizontallythrough an enclosure in WhlCh solid particulate material is applied, theoperation of the means shown in Figs. 1, 3, 4, 5 and 8 may beillustrated as follows: Slate particles, for instance, of a desiredmeshy are admitted from the hopper 65 into the chutes 29 on either sideof the sheet 35 in the enclosure. By keeping the chutes 29 full, theslate is continuously fed into the r. receptacles 1. The gates 4 areeach set, by means of *ously in substantially uniform concentrationthroughout its thickness and width in the plane at which the air blastfrom the compartment 13 strikes the particles and during a period ofcoating a sheet.

The 'air blast is fed from the conduit 54 through the connection 60, thevalve 57 being open and the valve 58 being closed; thence through theflue 22 and into the compartment 13 of each of the inclinedparticle-applying.

means. The blasts from these compartments are regulated by presettingthe air gates 14by means of the handwheels 17. Substantially at thecommencement of the vertical descent of the slate particles, a blast isapplied with substantially uniform force across the width of a stream,and will project the particles continuously toward the surfaces to becovered. The concentration of particles in the thus projected streamswill also be continuously substantially uniform during a given coatingoperation.

Though the Zones on a sheet to which the particles are applied whileintercepting the inclined streams from each of the receptacles 1 (asdescribed hereinabove) are overlapping, the sheets nevertheless becomeuniformly coated. It will be observed in Fig. 1, for instance, that whena sheet is moved from left to right through the projected streams theparticles from the lower end of a receptacle 1 will have covered thesheet surface before the particles from the upper end of a nextsubjacent receptacle reach the sheet. The latter particles are thereforedeflected by the particles previously bound to said surface of thesheet.

For the application of a solid particulate material like mica, forinstance, the valve 57 is closed, valve 58 is opened and the air blastpasses down the flue 46 and horizontally through the openings 48 acrossthe path of falling mica particles. The mica particles are therebyprojected toward the surface of a sheet passing through the tunnel 90.The quantity of mica continuously fed to the chutes 45 from the hopper66 is controlled by the speed of the belt conveyor 69. As previouslyindicated, the concentration of particles in the chutes 45 iscontinuously substantially uniform. The concentration of particles inthe stream passing through the slot 49 toward a sheet will also becontinuously substantially uniform. As the sheet, the surface of whichis maintained uniformly sticky over its entire area, is moved throughthe tunnel 90, it receives a substantially uniform coating of mica.

Particulate material that does not adhere to a sheet drops into the pit76 from which it is circulated by the conveyors 77 and 79, through thechute 82. Mica particles would drop from the chute 82 into the hopper73, gate 83 being open and gate 84 being closed. Overflow passes downthe chute 82 into a bin 98, or into bags 99. Make-up is also dumped intothe bin 98 from which the particles are passed into the pit forcirculation in the system. If particles of slate, for instance, areused, the gate 83 is closed and the gate 84 is open to feed the hopper65.

This application is a division of application Serial No.

783,710, filed November 3, 1947, now Patent 2,569,484. The invention ashereinabove set forth is embodied in particular form and manner but maybe variously embodied within the scope of the claims hereinafter made.

What is claimed is:

1. In a process of coating a sheet material with solid particulatematerial, which sheet material is precoated with an adhesive bondingmaterial, steps comprising: projecting particles of said particulatematerial horizontally in uniform suspension in gaseous streams forming aplurality of parallel, inclined superposed strata vertically spacedapart to the extent that the particles in the lower edge of any one ofsaid inclined strata above the lowermost stratum are below the particlesin the upper edge of the next subjacent stratum; and passinghorizontally said sheet material precoated with said adhesive bondingmaterial in vertical position in a plane crossing the paths of the saidstreams, the said strata being inclined with-respect to the horizontaldirection of travel of said sheet material, whereby the particles areapplied to a surface of said precoated sheet and uniformly coat the saidsurface.

2. Ina process of coating a sheet material with solid particulatematerial, which sheet material is precoated with an adhesive bondingmaterial, steps comprising: projecting particles of said particulatematerial horizontally in uniform suspension in gaseous streams forming aplurality of parallel, inclined superposed strata vertically spacedapartto the extent that the particles in the lower edge of any one ofsaid inclined strata above the lowermost stratum are below the particlesin the upper edge of the next subjacent stratum; and while maintaining asurface area of a coating of a thermoplastic bonding material on saidsheet material uniformly heated to maintain the said area substantiallyuniformly adhesive, passing horizontally said sheet material with saiduniformly adhesive surface in vertical position in a plane 8 crossingthe pathsof thesaid streams, the said strata being inclined with respectto the horizontal direction of travel of said sheet material, wherebythe particulate material is attached to the sheet and uniformly coatsthe sur ace.

References'Cited' in the file of this patent UNITED STATES PATENTS157,068 Edwards Nov. 24, 1874 1,003,441 Eaton Sept. 19, 1911 1,333,079Kaufmann Mar. 9, 1920 1,718,507 Wenzel et al. June 25, 1929 1,977,321Merritt etal. Oct. 16, 1934 2,139,619 Howell Dec. 6, 1938 2,141,658Melton-ct al. Dec; 27, 1938 2,235,978 Braucher Mar. 25, 1941 2,559,225Ransburg July 3, 1951

1. IN A PROCESS OF COATING A SHEET MATERIAL WITH SOLID PARTICULATEMATERIAL, WHICH SHEET MATERIAL IS PRECOATED WITH AN ADHESIVE BONDINGMATERIAL, STEPS COMPRISING: PROJECTING PARTICLES OF SAID PARTICULATEMATERIAL HORIZONTALLY IN UNIFORM SUSPENSION IN GASEOUS STREAMS FORMING APLURALITY OF PARALLEL, INCLINED SUPERPOSED STRATA VERTICALLY SPACEDAPART TO THE EXTENT THAT THE PARTICLES IN THE LOWER EDGE OF ANY ONE OFSAID INCLINED STRATA ABOVE THE LOWERMOST STRATUM ARE BELOW THE PARTICLESIN THE UPPER EDGE OF THE NEXT SUBJACENT STRATUM; AND PASSINGHORIZONTALLY SAID SHEET MATERIAL PRECOATED WITH SAID ADHESIVE BONDINGMATERIAL IN VERTICAL POSITION IN A PLANE CROSSING THE PATHS OF THE SAIDSTREAMS, THE SAID STRATA BEING INCLINED WITH RESPECT TO THE HORIZONTALDIRECTION OF TRAVEL OF SAID SHEET MATERIAL, WHEREBY THE PARTICLES AREAPPLIED TO A SURFACE OF SAID PRECOATED SHEET AND UNIFORMLY COAT THE SAIDSURFACE.